Microcirculation imaging

Abstract

An image is created of blood circulation deep (e.g. a plurality of millimeters) below the surface of living tissue to aid in evaluating a patient. A first beam (26) of circularly polarized light is directed forwardly (F) against an outer surface (14) of the tissue. Light that has penetrated to only a shallow depth before moving rearwardly and out of the tissue remains polarized and is blocked by a filter (38). Light that has penetrated to greater depths (12), is scattered more and becomes depolarized, and a portion of it passes through the depolarizing filter (38) and is focused on a photodetector (48) to create an image. Light spots (54) on the image that move, represent spaces between blood platelets (52) that are moving through a capillary, and indicates the velocity of blood through the capillary.

Description

BACKGROUND OF THE INVENTION[0001]There is a great need to determine whether or not there is sufficient perfusion, or blood circulation, in microvessels of a patient. Such microvessels include capillaries, arterioles and venules, which are herein all referred to as capillaries. Adequate microcirculation is vital for the transport of oxygen and other nutrients and the removal of waste. Distinctive microvascular pathologies are associated with different disease states such as in diabetes, hypertension, chronic heart disease, chronic ulcers and sepsis. One promising noninvasive technique is the shining of bright light at tissue and the detection of reflected and scattered light. However, it is found that this technique indicates microcirculation only at shallow depths of no more than about one millimeter below the tissue surface. It is known that circularly polarized light penetrates further into tissue than linearly or unpolarized light, but this has not led to better interrogation of ...

AI Technical Summary

Benefits of technology

The present invention provides a method and apparatus for sensing microcirculation at a depth of a plurality of millimeters below the surface of living tissue. The invention involves directing a first beam of circularly polarized light at the tissue and allowing it to penetrate the tissue. Some of the light reaches a boundary between materials of different indexes of refraction and is scattered. Some of the scattered light passes through a depolarizing filter that passes only depolarized light and is therefore largely depolarized. This allows the passage of a higher portion of deep light that has passed through the tissue, which is then imaged onto a photodetector. The output of the photodetector is used to generate an image that is largely of tissue at a depth of a plurality of millimeters below the surface of the tissue. The image changes with time and displays moving bright objects which represent spaces between blood platelets moving in one or more capillaries. The invention provides a novel way to sense microcirculation in living tissue.

Problems solved by technology

As a result, a considerable portion of such light passes through the depolarizing filter that passes only unpolarized light.

Images